As device and features size continue to shrink in the semiconductor industry, and also as 3D devices structures (e.g., Intel's Tri-Gate transistor architecture) become more prevalent in integrated circuit (IC) design, the capability of depositing thin conformal films (films of material having a uniform thickness relative to the shape of the underlying structure, even if non-planar) will continue to gain importance. Atomic layer deposition (ALD) is a film forming technique which is well-suited to the deposition of conformal films due to the fact that a single cycle of ALD only deposits a single thin layer of material, the thickness being limited by the amount of one or more film precursor reactants which may adsorb onto the substrate surface (i.e., forming an adsorption-limited layer) prior to the film-forming chemical reaction itself. Multiple “ALD cycles” may then be used to build up a film of the desired thickness, and since each layer is thin and conformal, the resulting film substantially conforms to the shape of the underlying devices structure.
The challenge with ALD, however, has to do with wafer processing throughput. Because each cycle of ALD only deposits one thin adsorption-limited layer, many cycles of ALD need to be performed in sequence to deposit a film of any desired appreciable thickness, and each cycle takes time. Accordingly, improved methods and apparatuses are sought to process wafers in parallel and thereby to improve wafer/substrate processing throughput in semiconductor fabrication operations.